Ships, fishnets or other underwater structures or equipments tend to attack aquatic organisms such as barnacles, mussels, and algae, and the like. Organisms can grow and multiply and eventually cause significant problems. For example, in the case of a ship's hull, the growth of marine organisms on the hull can increase the frictional resistance between the hull and water, thus increasing fuel consumption and reducing the speed of the ship.
One approach to the problems is to coat the surfaces of the structures with an antifouling coating in which a metal-containing polymer is present. These polymers normally have hydrolysable groups attached to the polymer backbone. Over time, the polymer at the outmost layer of the coating is hydrolyzed and becomes water erodible residue This residue is subsequently removed by water to provide a smooth, foul free surface. Such action is commonly referred to as a “self-polishing” effect.
Metal-containing self polishing copolymers have been in commercial use for many years. Since the ban on self-polishing tributyltin acrylate by the IMO, copper and zinc acrylates have become common polymers used in self polishing antifouling coatings.
Metal acrylates and methods of their preparation have been described in the literature.
Illustratively, U.S. Pat. No. 4,774,080 discloses a metal acrylate self polishing polymer obtained by reacting a copolymer with a monovalent organic acid and a metal oxide, chloride or hydroxide. Alternatively, the organic acid and metal salt can be replaced by a metal carboxylate. The copolymer used in the reaction can be obtained from the copolymerization of an unsaturated organic acid monomer and other polymerizable unsaturated monomers. Patent '080 also discloses that an unsaturated metal ester can first be prepared before copolymerizing with other unsaturated polymerizable monomers to provide a metal acrylate polymer. This reference is incorporated herein in its entirety.
U.S. Pat. No. 6,177,530, the disclosure of which is incorporated herein in its entirety, discloses a metal-containing hydrolysable copolymer obtained from the copolymerization of a metal-containing polymerizable monomer having two unsaturated groups and a metal-containing polymerizable monomer. Other polymerizable monomer can also be present.
Self-polishing polymers are used alone or in combination with other biocides to further enhance antifouling performance. When the polymers are used together with other biocides, the current practice is to prepare the polymers and the primary and supplemental biocides separately and then add them individually into antifouling paint compositions.
There is a need in the anti-fouling paint community for a cost effective process that can produce a mixture of metal-containing self polishing polymer and a booster biocide simultaneously. The present invention provides one answer to that need.